The present invention relates to a polyphase AC multiple step-up rectifier circuit for rectifying an output voltage from a secondary winding of a transformer and obtaining a high voltage by using a combination of capacitors and diodes.
Several conventional multiple step-up rectifier circuits have been proposed. However, these circuits serve to provide a DC high voltage from a single phase AC voltage. None of these can provide a DC high voltage from a polyphase AC voltage.
A great advantage can be obtained by minimizing the dielectric withstand voltage between the primary and secondary windings of the transformer of a high-voltage generating apparatus of this type. In particular, a small AC dielectric withstand voltage allows a decrease in corona discharge, which discharge shortens the service life of the transformer. Therefore, great efforts have been made by circuit designers and manufacturers to decrease the AC dielectric withstand voltage described above. Corona discharge is not decreased only by means of the physical characteristics of insulators, but also by slight changes in the manufacturing process. For this reason, it is very important to develop a technique for decreasing the above-mentioned dielectric withstand voltage from the viewpoint of industrial application. From another viewpoint, the high-voltage generating apparatus has conventionally been made compact by decreasing the size of a transformer and related component parts in a high frequency arrangement. However, an insulation gap for the dielectric withstand voltage between the input and output terminals is determined independently of the frequency. When a high-voltage generating apparatus is operated at a higher frequency (i.e., the size is further decreased), the insulation gap is increased, thereby preventing the production of a compact apparatus.